years and i've never seen these guys before. >> reporter: california oysters. although small and not too many, these oysters are sensitive to water quality. folks here believe it's a good sign. >> obviously, the water's getting better. quality's getting much improved, which is very nice. >> reporter: this hasn't always been the case. for over a hundred years, a shipyard operator across the river. and legend has it once in the 1940s, the water caught fire. that, combined with agricultural runoff in the napa valley created nasty water. downriver, matthew sears manages the 112-year-old vallejo yacht club. he says wildlife is returning. >> we get the seal, little juvenile seal who is constantly using our harbor for fishing. he gets the salmon, the striped bass, and they don't have a chance. he gets them every time. >> reporter: there's still a lot of work to be done, but these small critters are making a big splash. while these oysters are a good indicator that the napa river is getting better all the time, i still wouldn't eat 'em. in vallejo, don ford, cbs 5. >>> san francisco's top cop te
